Pipe couplings are often used to couple or join the ends of two lengths of pipe together. Many modern pipe couplings are cylindrical or tubular devices formed of a pliable material such as natural or synthetic rubber. The free ends of the pipes to be coupled are fit into respective sides of the pipe coupling, and generally, one of many types of pipe or hose clamp is used to compress the coupling to the exterior surface of the pipes being joined. Pipe couplings thus serve at least two purposes. The coupling both joins the free ends of two or more pipes together and seals the joint against leakage.
The drain and waste system of most modern construction is fabricated from PVC or CPVC pipe having various suitable diameters. Generally, the interior drain and waste lines will be joined to one or more larger waste lines which passes from the interior to the exterior of the building.
In contrast to the interior drain and waste lines, exterior waste pipes and sewer lines are generally fabricated from clay, cast iron, formed concrete or other non-plastic materials. The pipes used in exterior waste lines often have a somewhat different outside diameter from the waste lines exiting a building. A special pipe coupling may be used to join together two pipes having differing outside diameters or fabricated from different materials.
Element 10 of FIG. 2 is a typical pipe coupling which may be installed between the waste pipe exiting a building and the feeder pipe to an external sewer line. Prior art couplings typically have a flexible or pliable body which is sized to receive the dissimilar pipes at opposite ends. In addition, one or more pipe clamps may be associated with the body to secure and seal the coupling to the respective pipes. Since a typical prior art coupling has a flexible or pliable body the pipe ends can move with respect to each other or separate from each other in response to tension or shear forces which are typically present when the ground around the pipes subsides, a building settles or other forces are applied to the system. Relatively small lateral displacement between the respective pipe ends can cause a failure of the seal and furthermore can cause a pipe edge to be projected into the flow pathway which facilitates blockage at the joint. The inability of a typical flexible coupling to adequately support the joint between waste and sewer pipes or to effectively resist shear and tension forces placed on the pipes is the primary cause of the failure of this joint. Accordingly, a commonplace but expensive repair which is often necessary on the joint between interior waste lines and the exterior sewer system involves excavation of the failed joint, repositioning of the pipes and replacement of the coupling.
Certain types of reinforced couplings are known which may reduce, but typically will not eliminate the problems described above. For example, couplings with a stainless steel support sleeve associated with the pipe clamps are available. Known reinforced designs do not, however, typically provide adequate support to resist the large shear and tension forces applied to pipes when a building or the ground around the joint settles.
Plumbing and sewage contractors may also encase the entire joint in a quantity of concrete. This effectively stabilizes the joint; however, this solution is expensive and renders the joint between the pipes no longer accessible for service needs.
The present invention is directed toward overcoming one or more of the problems discussed above.